1. Field of the Invention
The invention relates to an impact generator for rotating a weight by means of a rotary member and striking a struck member with the weight, thereby continuously generating impact force for working.
2. Description of the Related Art
An impact generator is a device for continuously generating impact force (shock force). Such impact generator may be applied to a crusher for crushing concrete or hardened asphalt in a road construction, a building site and the like, a reaper for cutting off fruit and branches of plants, and a root cutter for cutting off roots of plants, for example.
By way of example, Japanese Laid-Open Patent Publication No. Hei 7-164351 has disclosed an impact generator according to the prior art. FIG. 5A is a transverse sectional view showing the impact generator D100 according to the prior art and FIG. 5B is a longitudinal sectional view showing the impact generator D100 according to the prior art. The impact generator D100 is applied to a reaper and serves to give continuous impact force to a cutting blade 191. The impact generator D100 converts rotating force transmitted from a power unit such as an engine into reciprocating impact force and transmits the reciprocating impact force to the cutting blade 191.
As shown in FIGS. 5A and 5B, the impact generator D100 comprises a rotary member 110 and a weight 130. The rotary member 110 is rotatably supported in a casing 150 by means of rotary shafts 111 and 112. The rotary member 110 has plate-shaped holding portions 113 and 114. The plate-shaped holding portions 113 and 114 are connected to each other through a connecting shaft portion 115. The connecting shaft portion 115 is positioned eccentrically from a center C100 of rotation of the rotary member 110. Elliptical holes 113a and 114a are formed on the plate-shaped holding portions 113 and 114, respectively. A cylindrical weight 130 is held in the holes 113a and 114a. The holes 113a and 114a have diameters which are larger than the diameter of the weight 130. Therefore, the weight 130 can freely move to some extent in the holes 113a and 114a. More specifically, the weight 130 is movably held by the rotary member 110.
When the weight 130 performs a circular motion around the rotary shafts 111 and 112 of the rotary member 110 by the rotation of the rotary member 110, the top of a tappet 192 positioned to interfere with the locus of the circular motion is struck with the weight 130. The tappet 192 is supported movably in an axial direction thereof (in a right and left direction in FIGS. 5A and 5B). Therefore, the tappet 192 is struck, thereby giving an impact to the cutting blade 191 positioned on the left of the tappet 192 in FIGS. 5A and 5B. Thus, when the rotary member 110 is rotated, continuous impact force is given to the cutting blade 191.
In the above-mentioned impact generator D100, the tappet 192 is struck with the weight 130, thereby generating the impact force. However, when the tappet 192 is struck with the weight 130, the weight 130 receives a reaction in a direction toward the center C100 of rotation of the rotary member 110 from the tappet 192. Then, the weight 130 collides with points P101 and P102 on internal walls defining the holes 113a and 114a which are the closest to the center C100 of rotation. By the collision, the rotary shafts 111 and 112 supporting the rotary member 110 and bearings 151 and 152 supporting the rotary shafts 111 and 112 receive a shock. Accordingly, the load capacities of the bearings 151 and 152 should be increased.
By the collision, moreover, great vibrations are also given to a machine (a reaper or the like) to which the impact generator is applied. Further for this reason, great noises are made in some cases.
In consideration of above-mentioned circumstances, it is an object of the invention to relieve a shock to be given to a rotary shaft of a rotary member and a bearing supporting the rotary shaft.
In order to solve the above-mentioned problems, the invention provides an impact generator comprising a rotary member rotatably supported by a rotary shaft for being rotated upon receipt of rotating force, a weight movably held by the rotary member for striking a struck member, and a shock absorber provided between the weight and the rotary member for absorbing, by elastic force, a shock generated between the weight and the rotary member.
According to the impact generator described above, the shock force generated between the weight and the rotary member is absorbed by the shock absorber. Consequently, the shock to be given to the rotary member can be relieved. Accordingly, it is also possible to relieve the shocks to be given to the rotary shaft supporting the rotary member and a bearing supporting the rotary shaft.
The shock absorber can be provided in any configuration if it is provided between the weight and the rotary member to absorb the shock therebetween. For example, the rotary member may have two plate-shaped holding portions provided in almost parallel with each other for holding the weight, and a connecting shaft portion for connecting the two plate-shaped holding portions in a position which is eccentric from the center of rotation of the rotary member, and the shock absorber may be provided between the weight and the connecting shaft portion.
Moreover, any shock absorber capable of absorbing a shock by elastic force can be employed. For example, the shock absorber may be constituted by a coil spring, and a supporting hole may be formed in the connecting shaft portion of the rotary member, fitting one of ends of the coil spring therein to support the coil spring.
These objects as well as other objects, features and advantages of the invention will become more apparent to those skilled in the art from the following description with reference to the accompanying drawings.